Painting bump maps

The ability to paint bump maps is really one of the hidden gems of Mudbox.You may think that that's redundant, like why would I want to paint a bump mapthat simulates surface detail when I'm in a sculpting program that lets meactually sculpt that detail physically?Well, there's one really good reason, and that's because to sculpt really finedetailed texture, you would have to subdivide a model to maybe well over10 million polygons in some cases.This becomes a problem because all those polygons eat up hard drive space,memory, and also take a lot more processor power to compute.

The result is that Mudbox could get bogged down.The solution is to paint that detail with a bump map instead, because TextureMaps are much more memory efficient than polygons.Let's jump in and see how this works. Let's open up the Basic Head.I am going to make a new texture channel here, and let's set it to Bump Map, andI am also going to make the Size fairly large, 4000, and let's also save it as aTIFF, 16 bit Floating Point, and OK.

Bump Maps are grayscale images, so wherever you paint with white it will bumpup and wherever you paint with black it will push in.Let me demonstrate.We will get the Paint Brush activated here, and I am just going to zoom in close.Let's shrink the brush a little bit, and let's see what happens.So I am painting with black, and it's pushing in. We could go over here andpaint with white, and notice it's going to bump up.If I paint with a neutral gray, watch what happens.

It's kind of like we are treating everything back to its neutral point.Let me just undo that to demonstrate something.Mudbox is displaying the shades of gray that we paint as bump, but sometimes itcan be helpful to look at the actual colors rather than the effect.To do this, right-click on the layer and pick Solo As Diffuse.What this is doing is showing us the texture channel with its raw colorinformation before it gets interpreted as bump.

With this mode on, notice that the Visibility icon turns yellow.This means that we are in Solo As Diffuse mode.Looking at the model, you can see the painting and the shades of gray, butthere's also this checkerboard pattern.This means that the layer is empty in those areas.All new paint layers start out being transparent, or empty of paint.Before we really get to work with painting bump maps, we should fill the wholething with a neutral gray.We can either paint the whole thing manually with the big brush or flatten toUVs base, and then Flood From Camera.

So I am just going to zoom out a little bit here and just get a big brush andjust paint the whole thing gray.Let's turn off this Solo as Diffuse mode and then right click on the layer andcome down to Unsolo. Now let's paint some bump.You can use most any of the painting tools to do it, and for the most part itbehaves just like sculpting.So I am just going to grab a white color here. Let's zoom in and shrink theBrush Size a bit, and here you can just paint with bump, and it feels just likesculpting for the most part. You can hold down Ctrl as you are then going toinvert to the opposite color. So it behaves very much like sculpting.

There are a few differences, however.Remember that you're painting with shades of gray, so since I'm painting withwhites, for example, right now once the bump channel is filled with white, itwon't go any higher.I am trying to click and paint right here, but it's already white, so it's already at maximum bump.Bump isn't meant for sculpting large-volume changes.It's best for fine surface detail.Now let's turn on the wireframe, Shift+F. Notice how the bump map is independentof the Mesh Density.

This is great because you can now sculpt fine details without actually having tosubdivide the mesh so much.So you can see I have shrunk my brush way down, and I can still sculpt very finedetails even though the mesh is nowhere close to the density. I would need tosculpt this type of detail directly onto the mesh.Let me just make a couple more strokes here.So now let's subdivide the model a couple of times and actually do somesculpting on this model to compare bump sculpting with real sculpting.

We've got 2 million polygons now.I am going to hit Shift+F to turn off the wireframe, and now let's go on toSculpt tools, and I will gray Wax here, and let's see what happens.So if I am sculpting with wax--actually that's really too much strength, and let mebring that Strength down, and maybe a little bit higher.Okay, so that's almost the same effect.So I am going to zoom in, and notice how when we move the camera to the side, youcan see that the sculpting we did with wax is actually deforming the surface,whereas the bump you can see--if we look at it from a very oblique angle--youcan see it's not actually changing the surface of the model, whereas sculptingwith wax can actually let me sculpt up rather than pushing in. You can see it isactually changing the surface of the model.

One last thing I want to mention is that when you paint with bump over a UVseam, it can look broken or disjointed. Let me show you what I mean.Let me go to the Paint Brush, and this model has a UV seam along the top of the headLet's see if we can find that. Okay, here it is.So you see this line right through here? That's where there is a UV seam on the model.Okay, we found another one right here.When you are painting in Mudbox with the bump map, you might see theselined along the UV seams. Don't worry it's just a Mudbox glitch.

If you export the map to another program, the bump will display without any seams visible.So painting bump maps can save you a lot of headache when sculpting finedetails, because you don't actually have to have a super-dense mesh just to get super-fine details.

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Author

Released

7/26/2012

This course introduces Mudbox, the Autodesk digital sculpting suite, and teaches digital artists how to create realistic assets in Mudbox, including 3D characters, immersive game environments, and product designs. Author Ryan Kittleson focuses on modeling, sculpting, and texturing, as well as topics such as extracting normal maps and exporting assets to Maya and 3ds Max for further rendering and animation. The final chapter covers techniques for showcasing your work in Mudbox.